Planar in-phase filtering power divider with tunable power division and controllable band for wireless communication systems

A wideband in-phase power divider with tunable power division ratio (PDR) and filtering response is presented. The proposed design is quite compact and consists of a three-line coupled structure and loaded with a pair of varactor-loaded short-ended stubs at two output terminations. A variable power division is realized by tuning the coupling factors between the centerline and sidelines of the three-line coupled structure using a pair of varactors. A varactor at the center of the loaded short-ended stub and another one connecting the end of the stub to the ground is used to control the center frequency and band of operation. A prototype is modeled using the microstrip technique and then simulated and tested. The experimental result indicates a tunability of PDR from 0.5:1 to 2:1 across wideband range of 60% and a controllable hand from 35% to 63.2%, with 13% center frequency tunability, sharp passband cutoff selectivity, as well as harmonic suppression to more than 6 GHz (4 times the center frequency). Moreover, the overall loss is around 1-1.2 dB; the isolation is more than 14 dB, whereas the differential phase is less than 7 degrees in all the investigated cases